At some point the level crashed for me. If you
experience the same, the solution is to use the original title.tr4 instead
of the one provided with the BtB package. There are more levels that had
this problem, like The Power of the Dragon and Canreggio, so you can use the
title.tr4 provided with these levels.

Sewers, the Crowbar.

Follow the current and swim into the first right,
climb out to the right and jump SW to a small ledge at the crossing of the
tunnels, shoot rats S and jump there, head over to the NW corner and find a
lever on the pillar E, it will close the doors in the canal, dive in and use
the underwater lever N (right under where you are). A ceiling hatch opens E,
climb out S and go to the E end of the tunnel, there’s a cross SE, leave it
be. Jump to the other side and push the cross NE away from the Crowbar.
Then get to the block at the hatch and climb up. Open the crowbar door and
follow to a square.

Go SW and into a small room where you can crawl
under the hanging laundry to a small medipack. Head E and then left
to come to a yard with 2 Gangsters. Get the Shotgun ammo from the
garbage bin E and step carefully behind the bin NE, use the lever on the
wall and get out. A door opened in the S wall. Inside is

Secret #1,
a Mysterious Rose and a Medipack. Go out again and get down
the manhole SE, get the Waterskin from the room below, fill it while you’re
down there. Leave the yard SW and go S, follow through and jump to the
jetty, shoot the Gangsters of which the white one drops a small medipack.
Go on and shoot more Gangsters, in the end is a closed door E.

The Carnival Mask.

First we retrace our steps a bit W a bit to the SW
corner of this passage, in the water is an opening S. Save and swim in high
and turn right you have to swim straight through the centre of those spike
traps. Into the opening straight ahead and left at that propeller, in the
back of that tunnel you can swim up facing S and use an underwater lever
there. Roll, swim down and S to get to the back of the propeller where
you’ll find the Carnival Mask. Now get back fast as the air runs out.
Back in the large tunnel go E.

The Glock 17.

Swim into the opening E, under the door, climb up
in a room. SW you can place the Mask on the stand and the door opens up. Go
into a room with a Fire Bowl. Down to the right of it is Glock ammo,
on the other side a Medipack you’ll need soon. You did fill the
Waterskin did you? Otherwise do it now.

Save one step from the burning bowl and be ready
for a run back to water while pumping Medipacks (you can use the numeric 0
and 9 keys, first for a small medi, the second for a large, maybe a wrong
kind of flame emitter was used here or this is just cruel) Step close to the
bowl and you’ll catch fire, put the fire out with the Waterskin and a
ceiling hatch opens op over the bowl. Roll and run to the water. Here the
level crashed for me (look at the top of the walk how to resolve this). Go
back in, climb up at the bowl and get the Glock 17 from the garbage
bin and a Medipack in the back. Go back down and out of the room to
the water.

Turbo Scooter.

Go W, hop onto the crates N. Pull the Timed
lever, hop back twice turning left a bit and then turn right a bit to hop
onto the timed platform, run forward and backflip to the room above. Get a
Medipack, Glock ammo and the Turbo Scooter.

Get down and back to the water and into to the N
and out in the open, to the bridge over the canal. There is a Medipack
around on the left if you jump in the water.

The Lasersight.

Go to the chain NE of the bridge. Up you go and
backflip onto a ledge next to the balcony, jump W to the awning. W again to
the stone pillar. Go inside and grab the Lasersight from the table.
Notice the harp.

Harp Puzzle, the Yellow Key.

Go down the hole in the floor and use the switch
on the crate to raise a platform. Open the crowbar door NE and follow the
stairs back up to the room with the harp, push it onto the raised platform
and go back down to flip the switch again. Get the harp and put it on the
tile next to the crate. A door opens upstairs. Go back up and in the passage
SW is the open door. Go in, jump up and grab the Yellow Key. Go out
and dive down into the canal, climb out N.

Shoot the Bells, 1 & 2.

Go into an alley NW, follow through up some blocks
and get some Glock ammo. Go back onto the bridge and look up W above
the big clock, 2 Bells. Shoot them with the Glock and Sight. Now go into an
alley all the way in the back SE, follow through to a steep part, stand left
and face the ladder, standjump and grab it, go up and left to get to the
higher part of the alley, follow down a slide. Down there you can grab up to
the right and shoot the window to get Secret #2,
another Mysterious Rose.

The Wires.

Get out and proceed to another part of the main
canal. The bridge is left through the underwater opening. Swim over to the
opposite side (N) and to the right is a fuse box, shoot the cover and pry
the Wires out of the box.

Shoot the Bells, 3 & 4.

Go stand on the other side (NW) of this jetty and
look up E, 2 more Bells. Shoot them and a door opens up in the N wall close
to you.

Storage Room, Red Wine, a Heart.

Grab up to the opening and shoot a Gangster in
that passage. Open the crowbar door N and step into a storage room. Go left
around the corner and to a crate, climb over it and head into the passage E,
timing the crates and spike bags. Make your way E and get Shotgun ammo.
To the left is a Bottle of Red Wine, crawl along the N wall to get
it. To the S are the Heart and the Shotgun and a small
medipack on a crate. Make your way back out of the Storage room.

Use the Heart, a Zip-Line.

Go up (S) and place the Heart at the gate, use the
zip-line to get to the ladder and climb up, go left (S) and jump over the
balustrade to the walkway, go to the left and find a lever around the
corner.

City Heating, place the Wires.

A gate opens under the building E, dive down and
swim in there. Climb out N, the open gate is NE. Time the steam blowers and
get the Glock ammo, in the end you can place the Wires in the pipe. A
door opens in a courtyard. Go out, swim NW through the big opening under the
building and the current will take you back to the bridge area, climb out S
near the wide passage.

The Blue Key, a Torch.

Hop over the crates and shoot some dogs. There’s a
small medipack on the grass. Near the big doors S is the lock for the
Yellow Key, but we need one more Key and that is in the building E where the
door opened. SE you can pick up some Glock ammo.

NE is a button behind that tree; push that now to
open the grate to the right (NE) there’s a burning garbage bin. Inside are 2
Gangsters, shoot them and get the Blue Key from the windowsill SW. In
the NE are Torches, pick one up and go out to that burning bin and carefully
ignite the Torch. Go back in, put the Wine in the Bowl and light it with the
Torch. A gate opens up S. Throw the lever there to lower 2 blocks with Harps
on top. A Demigirl appears, shoot her and get
Secret #3,
another Mysterious Rose.

Place the Harps, Exit.

Move both the Harps onto the white tiles W,
another block goes down revealing a button to open the door open again.

Into the House, open the Doors.

Use the 2 Keys in front of the house S and shoot
the Demigirl coming out. Go upstairs, move the table with the mirror to the
white tile W and a block goes up E. Climb it, open the ceiling hatch and
climb up E. Save before you slide down as there’s a nasty Blade below. I
slid down when the Blade was closed and came through ok. The next one is
more difficult, stand with your back to the W wall, as close to the Blade as
possible and now you can see it and time the sideflip over the Blade. Go on
and jump to the chandelier. To the next and from there to the window N. Go
outside and to the right is a button that will open the doors on ground
floor. Jump back to the chandelier and face NW to a crawlspace, it is too
far, but just to the left of it is a crack you can just reach with a grab in
the last moment. Get into the crawlspace to claim Secret #4,
another Mysterious Rose.

Open the Garage.

Get out and safety drop down to the stairs after
you went left on the crack. Go into the doors S. Shoot the Gangsters and
look for a Medipack behind the wall S (SE). Open the double doors W
and push the button to open the gate to the Vespa Scooter.

The Vespa Scooter.

Now you have to backtrack to the start of the
level, go out of the house to the canal and S at the bridge, Through the
underwater tunnel and follow the water to the end, go into the alleys and
keep going left till you see the Vespa straight ahead. When you use the
lever inside the garage, a grate opens. Shoot the Gangsters, mount the Turbo
on the Scooter and take it E and left to the small yard. Park it facing the
alley SE and get the Medipack from the alcove E (screenshot).

The Timed lever will start a flyby, showing
the route you will have to take with the Scooter.

The route is: Into the alley SE, turn right, right
around the next corner and speed up to jump the gap in the end onto the
jetty, follow the tunnels and through the now open door E, left out to the
bridge and take a sharp right there, to the end of this jetty and right into
the passage SE, up the steep part and down the slope around the corner, as
soon as you come outside, carefully right around the corners into the big
open doors. (the turbo wasn’t even
used much, only on 2 long stretches, you can jump corners, even with the
scooter.)

Leave the Scooter there and if you want to go back
at this point to look for missing Secrets, use the lever in the alcove E to
open the door back up (maybe you have to use it twice). Hop over the block
and go to a valve W, use it and the door opens up, this is the exit in case
you didn’t get the Secrets.

But we go for the last Secret, go into the room N
and place the 4 Roses on the central pillar, a block lowers. Hop on the
block and get

Secret #5,
the Code Card. Use that W and go into the opened curtain to get the
Final Rose from a beautiful Mirror room, the level ends after a nice
flyby.